Anne Kessler will use a portable oxygen concentrator, carried in a backpack, when she participates in the Gold Nugget Triathlon this weekend. Kessler has a form of interstitial lung disease. (Marc Lester / ADN)

After completing her first Gold Nugget Triathlon in 2009 when she was 61 years old, Anne Kessler made it a goal to keep doing the race until she was 70.

"I call it my annual physical," she said. "Last year I flunked big-time. This year I'm going to pass with the help of some accommodations."

Kessler, who turned 70 this year, skipped last year's race after being diagnosed with an interstitial lung disease called chronic hypersensitivity pneumonitis.

The condition, caused by allergens, takes her breath away — literally. When she hikes, bikes or does similar activities, scarring in her lungs limits the amount of oxygen that goes into her bloodstream and leaves her dangerously short of breath.

To compensate, Kessler wears a small, 6-pound backpack containing a portable oxygen concentrator (POC). The battery-operated device takes in air, filters out most of the nitrogen and delivers nearly pure oxygen into a long, narrow tube that Kessler breathes through.

Kessler received permission from Gold Nugget organizers to use the POC during the 12-mile bike and 3.5-mile run of Sunday's race.

During the 500-yard swim at the Bartlett High pool, Kessler will leave her backpack behind. She paid an extra fee to get an entire lane to herself, which will allow her to go at her own pace and make frequent stops.

"I used to swim in high school and college so the swim isn't worrisome, but there's no way I could wear my POC in the pool," Kessler said. "I'll go two laps and then stop for a full minute to catch my breath.

"So I'll add five minutes to my swim time, just to survive."

Kessler said she came up with the two-lap plan by using a fingertip oxygen monitor during workouts. She learned that after two laps her oxygen level would drop to 86 (88 or lower means it's time to use oxygen, she said). After a one-minute break, it would be up to 91 (above 90 is good, she said, although 95 or higher is preferred).

When in use, Kessler's POC backpack vibrates and emits a low, steady hum. "You have to really focus on getting in sync with the machine," she said.

Kessler's specific type of interstitial lung disease is caused by allergens — doctors suspect the culprit was either mold or bird feathers — and in her case is not reversible. But she can manage it with Prednisone and, when needed, the POC.

The POC allows her to remain active. Kessler likes to hike, bike and ski, and it was because she is active that she realized something was amiss a little more than a year ago.

"She found out through hiking," husband Steve Kessler said. "She couldn't keep up with anybody and she had to take breaks all the time."

Kessler spoke with a doctor, and X-rays and a CT scan revealed the disease a month before last year's Gold Nugget Triathlon.

"I missed the race," she said. "There were too (many) adjustments to make. And I went through denial. So I didn't do it.

"By January my life had settled down and I thought, 'Well, I'm going to try it.' ''

Kessler is confident she will complete the triathlon, although she isn't promising any speed records. She's pretty sure she'll have to stop at least once during the 12-mile bike, and she plans to walk, not run, the final 3.5 miles.

Kessler said that in the years since her first Gold Nugget Triathlon, she has fantasized about someday breaking into the top five in her age group. Before her diagnosis, she thought her best bet for such a result would come when she moved into the 70-74 age group, which has fewer participants than most others.

"I thought maybe when I'm 70 I could be in the top five, but now I don't care," Kessler said. "I want to finish, to say this (disease) didn't stop me."